Preparation And Properties Of Doped Calcium Borosilicate Glass-ceramics

The rapid development of modern electronic information technology requires that electronic equipment should be highly-integrated, highly-stable and with low loss, which put forward higher requirements to the LTCC substrate materials that are used in the electronic packaging technology. To explore new material systems and to modify the existing systems are currently research focus, which are guided by the market demand of LTCC substrate materials.Because of its good dielectric properties, low temperature sintering properties, similar themal expansion coefficient with silicon chips, good match with metal paste and effects of the reduction of high frequency signal relaxation, CaO-BiO₃/SiO₂ glass-ceramics is widely used in the field of microelectronics packaging. But CBS glass-ceramics still have some problems, for example, its density is deficient and it needs lower sintering temperature, which need further research. Changing properties by doping, this study aims to reduce the sintering temperature of CBS glass and improve the densities of CBS glass-ceramics. This study also aims to reveal the inherent laws that exist between its composition, microstructure and various properties after their properties are changed by additives. AlN are introduced to modify the thermal conductivities of CBS glass-ceramics. The influences of AlN on CBS glass-ceramics’densities and thermal conductivities are researched. Then use doping additives to improve AlN+CBS composites’densities.（1）Choose ZrO₂ as additive and study its effects on CBS glass-ceramics’ structures and properties. The study show that an appropriate amount of ZrO₂ can lower the CBS glass’crystallization temperature and appear CaSiO₃ sintered at 770℃. ZrO₂ as oxide of glass network intermediate also can reduce the viscosity of CBS glass, and promote the sintering process. When the wt （ZrO₂） is less than 7wt%, the increase of ZrO₂ can improve CBS glass-ceramics’ performances; wt （ZrO₂） is more than 7wt%, the increased amount of glass network intermediates will increase the CBS glass-ceramics’ resistivities, dielectric strengths and thermal conductivities.（2）With Al₂O₃ being doped, the structure and property of CBS glass-ceramics are studied. The results show:Al₂O₃ can suppress the crystallization of β-CaSiO₃, making β-CaSiO₃ change intoa-CaSiO₃; Al₂O₃ exists in the glass in the form of [AlO4] tetrahedron and [AlO₃]3- octahedron; Sintering properties and other properties are closely related to the adding quantity and sintering conditions; A moderate amount of Al₂O₃ can reduce the CBS glasses’ viscosities, improve the CBS glass-ceramics’ densities, decrease the CBS glasses’ sintering temperature, effectively control the number of [AlO₃]3- octahedral, prevent the increase of dielectric loss.Wt（Al₂O₃）=5% CBS glass sintering at 800℃ for 30 min get samples with optimal performance in every property.（3）The structure and properties of composite material, CBS+AIN, are studied. The results show:AIN can change the crystallization of CBS. As the mount of AIN increased, β-CaSiO₃ and Ca₂Si04 turned into CaAl₂Si208. When sintered at 900℃ for 30min, the sample,50wt%AlN+50wt%CBS, got the best density. Influenced by the density, AIN can only improve the thermal conductivity within a limited degree. A moderate addition of LiF and Al₂O₃ can improve the density of the composites. But LiF made the dielectric losses of the composites increase tremendously.